In automotive assemblies, for example oil filtration systems or other systems requiring circulation of a supply of cooling and/or lubricating fluid, special directional pipe unions are used to join or connect various components of the assembly and to redirect the fluid supply, often within a relatively compact space. Such pipe unions typically include a rotatable fluid coupling shaped to conduct fluid through the assembly and to redirect the flow in one or more lateral directions. When such couplings are configured with a rotatable body having a single right angled fluid port, they are commonly referred to as “banjo” unions or banjo couplings due to their banjo-like appearance, and once installed, referred to as banjo joints.
A banjo coupling is typically installed or attached to an external surface using a threaded fastener or bolt to form a banjo joint. The fastener includes a hollow shaft, with the hollow of the shaft forming a fluid channel suitable for conducting fluid through the banjo coupling from the external surface, or from the banjo coupling to the external surface, depending on the application. The shaft is typically formed with one or more lateral side ports or orifices that align with the right-angled fluid port of the banjo coupling, thereby redirecting the fluid through the banjo coupling as needed.
To facilitate assembly, banjo couplings are sometimes paired with a fastener in advance of installation to the external surface, and joined using a retaining clip or other such retaining device to prevent separation of the fastener and banjo coupling during shipping and handling prior to installation. Such clips are commonly designed to provide an interference fit with the threads of the fastener upon insertion of the fastener shaft through the banjo coupling so as to ensure that the clip firmly engages with the threads. However, interference fit designs may be less than optimal due to the sliding contact or friction occurring between the retaining device or clip and the various threads of the fastener as the fastener shaft passes through the retaining device.